全文获取类型
收费全文 | 5378篇 |
免费 | 134篇 |
国内免费 | 73篇 |
专业分类
化学 | 3093篇 |
晶体学 | 24篇 |
力学 | 258篇 |
数学 | 1010篇 |
物理学 | 1200篇 |
出版年
2023年 | 33篇 |
2022年 | 115篇 |
2021年 | 130篇 |
2020年 | 118篇 |
2019年 | 135篇 |
2018年 | 140篇 |
2017年 | 108篇 |
2016年 | 180篇 |
2015年 | 142篇 |
2014年 | 172篇 |
2013年 | 303篇 |
2012年 | 327篇 |
2011年 | 345篇 |
2010年 | 222篇 |
2009年 | 194篇 |
2008年 | 309篇 |
2007年 | 261篇 |
2006年 | 294篇 |
2005年 | 271篇 |
2004年 | 210篇 |
2003年 | 170篇 |
2002年 | 158篇 |
2001年 | 90篇 |
2000年 | 76篇 |
1999年 | 70篇 |
1998年 | 47篇 |
1997年 | 41篇 |
1996年 | 46篇 |
1995年 | 41篇 |
1994年 | 54篇 |
1993年 | 33篇 |
1992年 | 40篇 |
1991年 | 40篇 |
1990年 | 34篇 |
1989年 | 34篇 |
1988年 | 28篇 |
1987年 | 31篇 |
1986年 | 26篇 |
1985年 | 24篇 |
1983年 | 24篇 |
1982年 | 27篇 |
1980年 | 25篇 |
1979年 | 33篇 |
1977年 | 24篇 |
1976年 | 42篇 |
1975年 | 27篇 |
1974年 | 24篇 |
1973年 | 23篇 |
1972年 | 24篇 |
1967年 | 25篇 |
排序方式: 共有5585条查询结果,搜索用时 15 毫秒
81.
A. P. Klyagina I. F. Golovaneva G. G. Sadikov A. A. Levin 《Russian Chemical Bulletin》1990,39(8):1615-1617
A correlation between the stereochemistry and sign of the Cotton effect for * transition in the spectra of dimolybdenum tetracarboxylates and related compounds has been accomplished by constructing, within the framework of a one-electron model of optical activity, a 32-sector rule based on data from x-ray structure analysis and circular dichroism for dimolybdenum tetra-(R)-mandelate. It has been shown that a positive value of the pseudoscalar function xyz(x2–y2)(a2-z2) corresponds to a negative Cotton effect for the * transition in the case in which the dominant contribution to this effect comes from Rx components of the rotator strength of the transition.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1783–1785, August, 1990. 相似文献
82.
Within the resolution of the identity (RI) method, the convergence of the Hartree-Fock (HF) total molecular energy and the multipole moments in the course of the combined regular expansion of the molecular and auxiliary (RI) basis sets is studied. Dunning's cc-pVXZ series is used for both the molecular and the RI basis sets. The results show the calculated quantities converge to the HF limit when both the molecular and the RI basis sets are expanded from correlation-consistent polarized valence double zeta to correlation-consistent polarized valence sextuple zeta. Combinations of molecular/RI basis sets sufficient for convergence of the total energy and of the multipole moments at various accuracy levels have been determined. A measure of the RI basis set incompleteness is suggested and discussed. As it is significantly faster than the standard HF algorithm for small and midsize molecules, the RI-HF method, together with appropriate expanding series of both molecular and RI basis sets, provide an efficient tool to estimate and control the error of the Hartree-Fock calculations due to the finite basis set. 相似文献
83.
Vitalij V. Levin Pavel A. Belyakov Vladimir A. Tartakovsky 《Tetrahedron letters》2006,47(50):8959-8963
Nucleophilic addition of the pentafluorophenyl group from (C6F5)3SiF to non-activated imines affording α-C6F5-substituted secondary amines in high yield has been described. The reaction proceeds via simultaneous activation of imines and the silane reagent by means of a proton and chloride ion, respectively. 相似文献
84.
Igor Szczyrba 《Letters in Mathematical Physics》1980,4(3):249-256
For some family of representations of SU(n) the explicit formulae for the multiplicity of a given representation in arbitrary tensor product are derived. The adjoint representation and the representations acting in the symmetrical and antisymmetrical tensors are contained in the considered family as the simplest cases. 相似文献
85.
Igor Szczyrba 《Letters in Mathematical Physics》1981,5(5):449-457
The analogues of Gell-Mann-Okubo and Coleman-Glashow mass formulae are derived for arbitrary reductive Lie algebras. 相似文献
86.
Monitoring of ethanol during fermentation using a microbial biosensor with enhanced selectivity 总被引:1,自引:0,他引:1
Tkac J Vostiar I Gemeiner P Sturdik E 《Bioelectrochemistry (Amsterdam, Netherlands)》2002,56(1-2):127-129
The present study is concerning the construction of ferricyanide-mediated Gluconobacter oxydans cell ethanol biosensor. The size exclusion effect of a cellulose acetate membrane was used for elimination of glucose interferences during ethanol assays in real samples. A typical response time of the biosensor was 13 s with a high sensitivity of 3.5 microA mM(-1). The microbial biosensor exhibits a very low detection limit of 0.85 microM and a wide linear range from 2 to 270 microM. The operational stability was excellent. During 8.5 h of repetitive ethanol assays, no decrease in the sensor sensitivity was observed. The biosensor was successfully used in the off-line monitoring of ethanol fermentation with a good agreement with HPLC measurements (R(2)=0.998). 相似文献
87.
We present a new set of V–V rate coefficients for vibrational levels 0–5 in H2 at 300 K, measured using a stimulated Raman–spontaneous Raman pump/probe apparatus. The measured rate of the non-resonant process, H2(v = 1) + H2(v = 1) → H2(v = 0) + H2(v = 2), is consistent with the previously reported experimental value of Kreutz et al. However, semi-classical predictions of such non-resonant processes, using the identical inter-molecular potential and methodology to that given by Cacciatore and Billing, results in rates which are too slow, by a factor of approximately 3. For the “resonant” V–V process, H2(v = 1) + H2(v = 0) → H2(v = 0) + H2(v = 1), the semi-classical rate is found to be too slow by an even larger factor, of approximately 30, compared to the experimental rate, but consistent with the previously reported experimental result of Farrow and Chandler. Further, unlike the semi-classical model prediction in which the (1, 1 → 2, 0) process rate is predicted to exceed that of the (1, 0 → 0, 1) process, the experimental data shows it to be a factor of approximately 2.5 less, suggesting that semi-classical methods that treat the rotational motion classically are unsuitable for the highly anharmonic H2 molecule. The ratio of pure rotation and rotation–vibration Raman cross sections for scattering from levels 0 and 1 is also determined, with results which agree with calculations of Schwartz and LeRoy, but are somewhat larger than previous experimental results of Cureton. 相似文献
88.
Z. M. Khakimov F. T. Umarova N. T. Sulaymonov A. E. Kiv A. A. Levin 《International journal of quantum chemistry》2003,93(5):351-359
New model of Si? H bond dissociation is proposed and tested in the cluster Si10H16 by the simulation approach that combines classic molecular dynamics method and the self‐consistent tight‐binding electronic and total energy calculation one. It is shown that the monohydride Si? H bond is unstable with respect to silicon dangling bond and bend‐bridge Si? H? Si bond formation when this cluster traps the single positive charge and that hydrogen migrates through a path involving rather rotation around the Si? Si bond than the center of this bond (the bond‐centered position). These results can be useful for understanding hydrogen‐related phenomena at surfaces, interfaces, and internal voids of various hydrogenated silicon systems: electronic devices, silicon solar cells, and nanocrystalline and porous silicon. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 351–359, 2003 相似文献
89.
The electronic structure of all isomeric dihalobenzenes C6H4XY (X, Y = Cl, Br, I) has been investigated by HeI/HeII photoelectron spectroscopy, Green's functions calculations, and comparison with the spectra of related dihalobenzenes C6H4X2 (X = Cl, Br, I). The careful analysis of measured pi orbital and halogen lone pair ionization energies enabled us to describe substituent effects in terms of resonance, inductive, steric, and spin-orbit coupling interactions. 相似文献